Endoscopic surgery of a distensible organ, such as a uterus, may be performed with an endoscope that is insertable into the uterus through the cervix and a resector or other tool that passes through the endoscope to cut or otherwise treat tissue in the uterus. During surgery, it often is desirable to distend the uterus with a fluid, such as saline, sorbitol, or glycine, in order provide a visible working space. Fluid can be infused into the uterus and removed from the uterus through the endoscope and/or the resector.
If the outflow of fluid from the uterus is greater than the inflow of fluid to the uterus, the uterus may collapse back to its normal state, making visualization of the uterus difficult. On the other hand, if the inflow of fluid is greater than the outflow of fluid such that the pressure created by the fluid is greater than the patient's mean arterial pressure, excess fluid can enter the patient's vascular system (known as intravasation), which can lead to serious complications or injury.
The proximal end of the endoscope can include an access port for the working channel into which the resector can be inserted enabling the distal cutting end of the resector to travel through the working channel and beyond the distal end of the endoscope in the uterus to cut or otherwise treat tissue in the uterus. The distention fluid also enters the uterus through the working channel of the endoscope.
The endoscope can be used in two modes, diagnostic mode and operative mode. In diagnostic mode, the endoscope can be used to view inside the uterus in order to identify tissue to be removed or otherwise treated. In diagnostic mode, no resector or other tool is present in the working channel, however distention fluid is driven into the uterus to facilitate observation and diagnosis. In operative mode, the resector or other tool is present in the working channel and impedes the flow of distention fluid through the working channel into the uterus. The insertion or removal of the resector or other tool from the working channel can cause disruptive or dangerous changes in the distention of the uterus.
To avoid this problem, U.S. Pat. Nos. 8,062,214 and 8,419,626 disclose the use of two valves at the access port of the endoscope that can be used to control the flow impedance of distention fluid into the working channel of the endoscope. The first valve can be an on/off valve that controls the flow of distention fluid into the working channel of the endoscope. The second valve can be a two position valve that controls the flow impedance into the working channel. When the second valve is in a first position, the access port is open permitting the resector or other tool can be inserted through the working channel. In addition, second valve can be configured whereby it also allows unimpeded flow of the distention fluid into the working channel where it is impeded by the resector or other tool in the working channel. When the second valve is in a second position, the access port is closed whereby the resector or other tool cannot be inserted into the working channel. However, in the second position, the second valve is configured to allow the distention fluid to flow through a smaller orifice that approximates the impedance produced when the resector or other tool is present in the working channel. As a result, the fluid impedance is substantially the same regardless of whether the resector or other tool is present in the working channel and the position of the second valve which helps to reduce the risks associated with larger changes in distention fluid pressure.